Transmission method, reception method, transmission apparatus, and reception apparatus

ABSTRACT

A transmission method includes generating one or more frames for content transfer using IP packets, and transmitting the one or more generated frames by broadcast. Each of the one or more frames contains a plurality of second transfer units, each of the plurality of second transfer units contains one or more first transfer units, each of the one or more first transfer units contains at least one of the IP packets, an object IP packet of the IP packets contains first reference clock information indicating time for reproduction of the content in data structure different from MMT packet data structure, the object IP packet being stored in a first transfer unit positioned at a head in the one or more frames, the one or more frames contains control information storing second reference clock information indicating time for reproduction of the content, and header compression processing on the object IP packet is omitted.

BACKGROUND 1. Technical Field

The present disclosure relates to a transmission method and the like fortransmitting the content through broadcast by using IP (InternetProtocol) packets.

2. Description of the Related Art

An MMT (MPEG Media Transport) scheme (refer to NPTL 1) is a multiplexingscheme for multiplexing and packetizing content such as video and voiceand for transmitting the content through one or more transfer channelssuch as broadcast and broadband. When the MMT scheme is applied tobroadcasting systems, reference clock information of a transmissionapparatus is transmitted to a reception apparatus, and the receptionapparatus generates a system clock in the reception apparatus based onthe reference clock information.

CITATION LIST Non-Patent Literature

NPTL 1: Information technology-High efficiency coding and media deliveryin heterogeneous environments-Part 1: MPEG media transport (MMT),ISO/IEC FDIS 23008-1

SUMMARY

In one general aspect, the techniques disclosed here feature atransmission method including: generating one or more frames for contenttransfer using IP (Internet Protocol) packets; and transmitting the oneor more generated frames by broadcast, wherein each of the one or moreframes contains a plurality of second transfer units, each of theplurality of second transfer units contains one or more first transferunits, each of the one or more first transfer units contains at leastone of the IP packets, an object IP packet of the IP packets containsfirst reference clock information that indicates time for reproductionof the content in data structure different from data structure of an MMT(MPEG Media Transport) packet, the object IP packet being stored in afirst transfer unit positioned at a head in the one or more frames, theone or more frames contains control information in which secondreference clock information that indicates time for reproduction of thecontent is stored, and header compression processing on the object IPpacket is omitted.

Additional benefits and advantages of the disclosed embodiments willbecome apparent from the specification and drawings. The benefits and/oradvantages may be individually obtained by the various embodiments andfeatures of the specification and drawings, which need not all beprovided in order to obtain one or more of such benefits and/oradvantages.

It should be noted that general or specific embodiments may beimplemented as a system, a method, an integrated circuit, a computerprogram, a storage medium, or any selective combination thereof.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a diagram illustrating a protocol stack for performingtransfer using an MMT scheme and an advanced BS transfer scheme;

FIG. 2 is a diagram illustrating data structure of a TLV packet;

FIG. 3 is a block diagram illustrating a basic configuration of areception apparatus;

FIG. 4 is a block diagram illustrating a functional configuration of thereception apparatus when reference clock information is stored in anextension field of an MMT packet header;

FIG. 5 is a diagram illustrating an acquisition flow of the referenceclock information performed by the reception apparatus when thereference clock information is stored in the extension field of the MMTpacket header;

FIG. 6 is a block diagram illustrating the functional configuration ofthe reception apparatus when the reference clock information is storedin control information;

FIG. 7 is a diagram illustrating the acquisition flow of the referenceclock information performed by the reception apparatus when thereference clock information is stored in the control information;

FIG. 8 is a block diagram illustrating the configuration of thereception apparatus when the reference clock information is stored inthe TLV packet;

FIG. 9 is a diagram illustrating an example in which a long-format NTPis stored in the TLV packet;

FIG. 10 is a diagram illustrating the acquisition flow of the referenceclock information performed by the reception apparatus when thereference clock information is stored in the TLV packet;

FIG. 11 is a diagram illustrating structure in which the reference clockinformation is appended immediately before an IP packet header;

FIG. 12 is a diagram illustrating structure in which the reference clockinformation is appended immediately before the TLV packet;

FIG. 13 is a diagram illustrating structure of a transfer slot;

FIG. 14 is a diagram illustrating structure of a slot header of thetransfer slot;

FIG. 15 is a diagram illustrating an example in which a flag is storedin an undefined area of the slot header;

FIG. 16 is a diagram illustrating structure of TMCC control informationunder a transfer scheme for advanced broadband satellite digitalbroadcast;

FIG. 17 is a diagram illustrating stream classification/relative streaminformation of the TMCC control information;

FIG. 18 is a diagram illustrating an example in which the referenceclock information is stored in an undefined field of the slot header;

FIG. 19 is a block diagram illustrating the functional configuration ofthe reception apparatus when information indicating that the referenceclock information is contained within the slot header is stored in TMCCcontrol information;

FIG. 20 is a diagram illustrating the acquisition flow of the referenceclock information when the information indicating that the referenceclock information is contained in the slot header is stored in the TMCCcontrol information;

FIG. 21 is a diagram illustrating a flow of extracting a bit string at aspecific position from the IP packet or compressed IP packet;

FIG. 22A is a diagram illustrating an example of structure of TMCCextension information;

FIG. 22B is a diagram illustrating another example of structures of TMCCextension information;

FIG. 23 is a diagram illustrating an example of data structure of anextension area in which an extension classification classified in thisway is used;

FIG. 24A is a diagram illustrating an example of syntax when theextension classification is used;

FIG. 24B is a diagram illustrating another example of syntax when theextension classification is used;

FIG. 25 is a block diagram illustrating a functional configuration of areception apparatus according to a second exemplary embodiment;

FIG. 26 is a diagram illustrating an operation flow of the receptionapparatus according to the second exemplary embodiment;

FIG. 27 is a diagram schematically illustrating an example in which thereference clock information is stored in each of a plurality of layers;

FIG. 28 is a diagram schematically illustrating an example in which aplurality of pieces of the reference clock information is stored in onelayer;

FIG. 29 is a block diagram for describing an example in which pieces ofdata of different broadcasting station apparatuses are stored inseparate streams;

FIG. 30 is a diagram for describing a transmission method of differenceinformation;

FIG. 31 is a diagram for describing a variation of the transmissionmethod of the difference information;

FIG. 32 is a block diagram illustrating a functional configuration of areception apparatus according to a third exemplary embodiment;

FIG. 33 is a diagram illustrating an operation flow of the receptionapparatus according to the third exemplary embodiment;

FIG. 34 is a diagram illustrating another operation flow of thereception apparatus according to the third exemplary embodiment;

FIG. 35 is a block diagram illustrating a functional configuration of atransmission apparatus; and

FIG. 36 is a diagram illustrating an operation flow of the transmissionapparatus.

DETAILED DESCRIPTION

(Underlying Knowledge Forming Basis of the Present Disclosure)

The present disclosure relates to a method and apparatus in which areception apparatus receives reference clock information transmittedfrom a transmission apparatus and generates (reproduces) a referenceclock in a hybrid delivery system using an MMT (MPEG Media Transport)scheme which is under standardization by MPEG (Moving Picture ExpertGroup).

The MMT scheme is a multiplexing scheme for multiplexing and packetizingvideo and voice to transmit the video and voice via one or more transferchannels, such as broadcast and broadband.

When the MMT scheme is applied to a broadcasting system, the referenceclock of the transmission apparatus is synchronized with an NTP (NetworkTime Protocol) prescribed by IETF RFC 5905, and based on the referenceclock, a time stamp such as PTS (Presentation Time Stamp) and DTS(Decode Time Stamp) is added to a medium. Furthermore, the transmissionapparatus transmits the reference clock information to the receptionapparatus, and the reception apparatus generates the reference clock(hereinafter referred to as a system clock) in the reception apparatusbased on the reference clock information.

In the broadcasting system, a 64-bit long-format NTP capable ofindicating absolute time is preferably used as the reference clockinformation. However, although the conventional MMT scheme prescribesstoring a 32-bit short-format NTP in an MMT packet header andtransferring the 32-bit short-format NTP, the conventional MMT schemedoes not prescribe transferring the long-format NTP, and it is difficultfor a receiver apparatus to acquire high-precision reference clockinformation.

In contrast, control information, such as a message, a table, and adescriptor, is defined using the long-format NTP. It is possible toappend the MMT packet header to the control information for transfer. AnMMT packet, which is the control information to which the MMT packetheader is appended, is stored in an IP packet, and is transferredthrough a broadcast transfer channel or a broadband transfer channel.

When the MMT packet is transferred using an advanced BS transfer schemeprescribed by the ARIB standard (STD-B44: transfer scheme of an advancedbroadband satellite digital broadcast), after encapsulation of the MMTpacket into the IP packet and encapsulation of the IP packet into a TLV(Type Length Value) packet, the MMT packet is stored in a transfer slotprescribed by the advanced BS transfer scheme.

However, when the transmission apparatus stores the reference clockinformation in an MMT packet layer, in order to obtain the referenceclock information, the reception apparatus extracts the TLV packet fromthe transfer slot, extracts the IP packet from the TLV packet, extractsthe MMT packet from the IP packet, and further extracts the referenceclock information from the header or a payload of the MMT packet.Therefore, the reception apparatus involves many processes for acquiringthe reference clock information, and needs longer time until theacquisition.

In addition, processes in layers equal to or higher than an IP layer aresoftware processes. Accordingly, when the reference clock information isstored in the MMT packet, the reference clock information is extractedand reproduced by a software program. Therefore, the reference clockinformation to be acquired may contain jitter depending on throughput ofa CPU, interruption by and priority of other software programs, and thelike.

Therefore, a transmission method according to one aspect of the presentdisclosure includes: generating one or more frames for content transferusing Internet Protocol (IP) packets; and transmitting the one or moregenerated frames by broadcast, wherein each of the one or more framescontains a plurality of second transfer units, each of the plurality ofsecond transfer units contains one or more first transfer units, each ofthe one or more first transfer units contains at least one of the IPpackets, an object IP packet of the IP packets contains first referenceclock information that indicates time for reproduction of the content indata structure different from data structure of a MPEG Media Transport(MMT) packet, the object IP packet being stored in a first transfer unitpositioned at a head in the one or more frames, the one or more framescontains control information in which second reference clock informationthat indicates time for reproduction of the content is stored, andheader compression processing on the object IP packet is omitted.

Thus, with the reference clock information (first reference clockinformation) contained in the TLV packet positioned at a head within thetransfer slot, the reception apparatus can specify a position of thereference clock information in advance. Therefore, the receptionapparatus can reduce (simplify) processes for acquiring the referenceclock information. Here, an example of the first transfer unit is a TLVpacket, an example of the second transfer unit is a slot, and an exampleof the transfer frame is a transfer slot.

In addition, by the transmission apparatus prescribing presence ofheader compression of the IP packet, the reception apparatus can specifythe position of the reference clock information in more detail. Such aconfiguration can also simplify the process by which the receptionapparatus acquires the reference clock information.

Furthermore, by the second reference clock information that indicatestime for reproduction of the content being stored in the controlinformation within the frame, the reception apparatus can select whichreference clock information to use from among the first reference clockinformation and the second reference clock information.

In addition, the control information may be Transmission andMultiplexing Configuration Control (TMCC).

In addition, the content may be stored in the MMT packet within each ofthe IP packets.

In addition, each of the first transfer units may be a variable-lengthtransfer unit, and each of the second transfer units may be afixed-length transfer unit.

In addition, each of the first transfer units may be a Type Length Value(TLV) packet, each of the second transfer units may be a slot under atransfer scheme for advanced broadband satellite digital broadcast, andeach of the frames may be a transfer slot under the transfer scheme foradvanced broadband satellite digital broadcast.

In addition, the reference clock information may be a Network TimeProtocol (NTP).

In addition, the frame may be transmitted in a predeterminedtransmission cycle.

A reception method according to one aspect of the present disclosureincludes: receiving by broadcast one or more frames for content transferusing Internet Protocol (IP) packets, the one or more frames storingfirst reference clock information and second reference clockinformation; extracting at least one piece of the first reference clockinformation and the second reference clock information from the receivedone or more frames; and generating a clock for reproducing the contentby using the at least one piece of extracted reference clockinformation, wherein each of the one or more frames contains a pluralityof second transfer units, each of the plurality of second transfer unitscontains one or more first transfer units, each of the one or more firsttransfer units contains at least one of the IP packets, the firstreference clock information is contained in an IP packet of the IPpackets which is stored in a first transfer unit positioned at a head inthe one or more frames, the first reference clock information havingdata structure different from data structure of a MPEG Media Transport(MMT) packet, header compression processing is omitted on the IP packetin which the first reference clock information is stored, and the secondreference clock information is stored in control information containedin each of the one or more frames.

A transmission apparatus according to one aspect of the presentdisclosure includes: generating circuitry which, in operation, generatesone or more frames for content transfer using Internet Protocol (IP)packets; and transmitting circuitry which, in operation, transmits theone or more generated frames by broadcast, wherein each of the one ormore frames contains a plurality of second transfer units, each of theplurality of second transfer units contains one or more first transferunits, each of the one or more first transfer units contains at leastone of the IP packets, an object IP packet of the IP packets which isstored in a first transfer unit positioned at a head in the one or moreframes contains first reference clock information that indicates timefor reproduction of the content in data structure different from datastructure of a MPEG Media Transport (MMT) packet, the one or more framescontains control information in which second reference clock informationthat indicates time for reproduction of the content is stored in thecontrol information, and header compression processing on the object IPpacket is omitted.

A reception apparatus according to one aspect of the present disclosureincludes: receiving circuitry which, in operation, receives by broadcastone or more frames for content transfer using Internet Protocol (IP)packets, the one or more frames storing first reference clockinformation and second reference clock information; extracting circuitrywhich, in operation, extracts at least one piece of the first referenceclock information and the second reference clock information from thereceived one or more frames; and generating circuitry which, inoperation, generates a clock for reproducing the content by using the atleast one piece of extracted reference clock information, wherein eachof the one or more frames contains a plurality of second transfer units,each of the plurality of second transfer units contains one or morefirst transfer units, each of the one or more first transfer unitscontains at least one of the IP packets, the first reference clockinformation is contained in an IP packet of the IP packets which isstored in a first transfer unit positioned at a head in the one or moreframes, the first reference clock information having data structuredifferent from data structure of a MPEG Media Transport (MMT) packet,header compression processing is omitted on the IP packet in which thefirst reference clock information is stored, and the second referenceclock information is stored in control information contained in each ofthe one or more frames.

Note that these general or specific aspects may be implemented using asystem, an apparatus, a method, an integrated circuit, a computerprogram, or a computer-readable recording medium such as a CD-ROM. Also,these general or specific aspects may be implemented using anycombination of a system, an apparatus, a method, an integrated circuit,a computer program, and a recording medium.

Exemplary embodiments will be specifically described below withreference to the drawings.

Note that each of the exemplary embodiments below describes acomprehensive or specific example. Numerical values, shapes, materials,elements, arranged positions and connection forms of the elements,steps, the order of the steps, and the like described in the followingexemplary embodiments are merely an example, and do not intend to limitthe present disclosure. Also, among elements described in the followingexemplary embodiments, elements that are not included in an independentclaim which represents the highest concept are described as optionalelements.

FIRST EXEMPLARY EMBODIMENT

[Basic Configuration of an MMT Scheme]

First, a basic configuration of an MMT scheme will be described. FIG. 1illustrates a protocol stack diagram for performing transfer using theMMT scheme and an advanced BS transfer scheme.

Under the MMT scheme, information such as video and voice is stored in aplurality of MPUs (Media Presentation Units) and a plurality of MFUs(Media Fragment Units), and is MMT-packetized with an MMT packet headerbeing added.

Meanwhile, under the MMT scheme, the control information such as an MMTmessage is MMT-packetized with the MMT packet header being added. TheMMT packet header is provided with a field that stores a 32-bitshort-format NTP, and this field may be used for QoS control ofcommunication lines, etc.

MMT-packetized data is encapsulated into an IP packet having a UDPheader or IP header. At this time, in the IP header or UDP header, whena set of packets with an identical source IP address, destination IPaddress, source port number, destination port number, and protocolclassification is an IP data flow, headers of the plurality of IPpackets contained in one IP data flow are redundant. Therefore, headercompression of some IP packets is performed in one IP data flow.

Next, a TLV packet will be described in detail. FIG. 2 is a diagramillustrating data structure of the TLV packet.

As illustrated in FIG. 2 , the TLV packet stores an IPv4 packet, IPv6packet, compressed IP packet, NULL packet, and transfer control signal.These pieces of information are identified using an 8-bit data type.Examples of the transfer control signal include an AMT (Address MapTable) and NIT (Network Information Table). In addition, in the TLVpacket, a data length (byte unit) is indicated using a 16-bit field, anda value of data is stored after the data length. Since there is 1-byteheader information before the data type (not illustrated in FIG. 2 ),the TLV packet has a total of 4-byte header area.

The TLV packet is mapped to a transfer slot under the advanced BStransfer scheme. Pointer/slot information that indicates a head positionof a first packet and a tail position of a last packet which arecontained in every slot are stored in TMCC (Transmission andMultiplexing Configuration Control) control information (controlsignal).

Next, a configuration of a reception apparatus when the MMT packet istransferred by using the advanced BS transfer scheme will be described.FIG. 3 is a block diagram illustrating the basic configuration of thereception apparatus. Note that the configuration of the receptionapparatus of FIG. 3 is simplified. More specific configuration will bedescribed later individually according to a manner in which referenceclock information is stored.

Reception apparatus 20 includes receiver 10, decoder 11, TLVdemultiplexer (DEMUX) 12, IP demultiplexer (DEMUX) 13, and MMTdemultiplexer (DEMUX) 14.

Receiver 10 receives transfer channel coded data.

Decoder 11 decodes the transfer channel coded data received by receiver10, applies error correction and the like, and extracts the TMCC controlinformation and TLV data. The TLV data extracted by decoder 11 undergoesDEMUX processing by TLV demultiplexer 12.

The DEMUX process performed by TLV demultiplexer 12 differs according tothe data type. For example, when the data type is a compressed IPpacket, TLV demultiplexer 12 performs processes such as decompressingthe compressed header and passing the header to an IP layer.

IP demultiplexer 13 performs processing such as header analysis of an IPpacket or UDP packet, and extracts the MMT packet for each IP data flow.

MMT demultiplexer 14 performs a filtering process (MMT packet filtering)based on a packet ID stored in the MMT packet header.

[Method for Storing the Reference Clock Information in the MMT Packet]

Under the MMT scheme described with reference to FIG. 1 to FIG. 3described above, although the 32-bit short-format NTP can be stored inthe MMT packet header for transfer, there exists no method fortransferring a long-format NTP.

Hereinafter, a method for storing the reference clock information in theMMT packet will be described. First, the method for storing thereference clock information within the MMT packet will be described.

When the control information that defines a descriptor, a table, or amessage for storing the reference clock information is stored in the MMTpacket, the descriptor indicating the reference clock information and anidentifier indicating the table or message are indicated within thecontrol information. Then, the control information is stored in the MMTpacket in the transmission apparatus.

This allows reception apparatus 20 to identify the reference clockinformation based on the identifier. Note that the reference clockinformation may be stored in the MMT packet by using existingdescriptors (for example, CRI_descriptor( ), etc.).

Next, a method for storing the reference clock information in the MMTpacket header will be described.

For example, there is a method for storing the reference clockinformation by using a header_extension field (hereinafter referred toas an extension field). The extension field becomes effective when anextension_flag of the MMT packet header is set to ‘1’.

An extension field type indicating data classification of data to bestored in the extension field is stored in the extension field.Information indicating that the data is reference clock information (forexample, a 64-bit long-format NTP) is stored in the extension fieldtype. The reference clock information is stored in the extension field.

When header_extension_flag of the MMT packet header is ‘1’, receptionapparatus 20 refers to the extension field of the MMT packet. When theextension field type indicates that the data is reference clockinformation, reception apparatus 20 extracts the reference clockinformation and reproduces a clock.

Note that the reference clock information may be stored in an existingheader field. In addition, when there is an unused field or when thereis a field unnecessary for broadcast, the reference clock informationmay be stored in these fields.

In addition, the reference clock information may be stored by using theexisting field and the extension field together. For example, theexisting 32-bit short-format NTP field and the extension field may beused together.

Regarding the reference clock information, in order to maintaincompatibility with an existing field, of the 64-bit long-format NTP, a32-bit section corresponding to a short-format format may be stored inthe existing field, and remaining 32 bits may be stored in the extensionfield.

Here, the reference clock information is, for example, time when a headbit of the MMT packet in which the reference clock information is storedpasses a predetermined position (for example, when the head bit isoutput from a specific component of a transmission apparatus). However,the reference clock information may be time when a bit of anotherposition passes the predetermined position.

When the reference clock information is stored in the MMT packet as thecontrol information, the MMT packet containing the control informationis transmitted at predetermined transmission intervals.

When the reference clock information is stored in the extension field ofthe MMT packet, the reference clock information is stored in theextension field of a predetermined MMT packet header. Specifically, forexample, at least one or more pieces of the reference clock informationare stored in the header extension fields of the MMT packets atintervals of 100 ms.

Note that, when the reference clock information is stored in the MMTpacket, the packet ID of the MMT packet that stores the reference clockinformation is stored in program information. Reception apparatus 20analyzes the program information and acquires the MMT packet in whichthe reference clock information is stored. At this time, the packet IDof the MMT packet in which the reference clock information is stored maybe prescribed in advance as a fixed value. This allows receptionapparatus 20 to acquire the reference clock information withoutanalyzing the program information.

[Operation Flow when the Reference Clock Information is Stored in theMMT Packet]

Next, an operation flow when the reference clock information is storedin the MMT packet (acquisition flow of the reference clock information)will be described.

First, the following describes the acquisition flow of the referenceclock information performed by reception apparatus 20 when the referenceclock information is stored in the extension field of the MMT packetheader. FIG. 4 is a block diagram illustrating a functionalconfiguration of reception apparatus 20 when the reference clockinformation is stored in the extension field of the MMT packet header.FIG. 5 is a diagram illustrating the acquisition flow of the referenceclock information performed by reception apparatus 20 when the referenceclock information is stored in the extension field of the MMT packetheader.

In FIG. 4 , when the reference clock information is stored in theextension field of the MMT packet header, MMT demultiplexer 14 includesreference clock information extractor 15 (an example of an extractor),and reference clock generator 16 (an example of a generator) is provideddownstream of MMT demultiplexer 14.

In the flow of FIG. 5 , decoder 11 of reception apparatus 20 decodes thetransfer channel coded data received by receiver 10 (S101), and extractsthe TLV packet from the transfer slot (S102).

Next, TLV demultiplexer 12 performs DEMUX on the extracted TLV packet toextract the IP packet (S103). At this time, the header of the compressedIP packet is reproduced.

Next, IP demultiplexer 13 performs DEMUX on the IP packet, acquires thespecified IP data flow, and extracts the MMT packet (S104).

Next, MMT demultiplexer 14 analyzes the header of the MMT packet, anddetermines whether the extension field is used and whether the referenceclock information is in the extension field (S106). When there is noreference clock information in the extension field (No in S106), theprocess ends.

On the other hand, when the determination is made such that thereference clock information is in the extension field (Yes in S106),reference clock information extractor 15 extracts the reference clockinformation from the extension field (S107). Then, reference clockgenerator 16 generates the system clock based on the extracted referenceclock information (S108). The system clock is, in other words, a clockfor reproducing content.

Next, the acquisition flow of the reference clock information byreception apparatus 20 when the reference clock information is stored inthe control information will be described. FIG. 6 is a block diagramillustrating the functional configuration of reception apparatus 20 whenthe reference clock information is stored in the control information.FIG. 7 is a diagram illustrating the acquisition flow of the referenceclock information performed by reception apparatus 20 when the referenceclock information is stored in the control information.

As illustrated in FIG. 6 , when the reference clock information isstored in the control information, reference clock information extractor15 is disposed downstream of MMT demultiplexer 14.

In the flow of FIG. 7 , the processes of step S111 to step S114 areidentical to the flow of step S101 to step S104 described in FIG. 5 .

Subsequently to step S114, MMT demultiplexer 14 acquires the packet IDof the packet containing the reference clock information from theprogram information (S115), and acquires the MMT packet of the packet ID(S116). Subsequently, reference clock information extractor 15 extractsthe reference clock information from the control signal contained in theextracted MMT packet (S117), and reference clock generator 16 generatesthe system clock based on the extracted reference clock information(S118).

[Method for Storing the Reference Clock Information in the TLV Packet]

As described in FIG. 5 and FIG. 7 , when the reference clock informationis stored in the MMT packet, in order that the reception apparatusobtains the reference clock information, reception apparatus 20 extractsthe TLV packet from the transfer slot, and extracts the IP packet fromthe TLV packet.

Furthermore, reception apparatus 20 extracts the MMT packet from the IPpacket, and further extracts the reference clock information from theheader or a payload of the MMT packet. When the reference clockinformation is stored in the MMT packet, reception apparatus 20 has manyprocesses for acquiring the reference clock information, and much timeis required until the acquisition, which needs to be addressed.

Therefore, a method will be described for implementing a process ofadding a time stamp to a medium, such as video and voice, based on thereference clock, and a process of transferring the medium by using theMMT scheme, and for performing transfer of the reference clockinformation by using a lower layer, lower protocol, or lowermultiplexing scheme than the MMT layer.

First, a method for storing the reference clock information in the TLVpacket for transfer will be described. FIG. 8 is a block diagramillustrating the configuration of reception apparatus 20 when thereference clock information is stored in the TLV packet.

Reception apparatus 20 in FIG. 8 differs from reception apparatus 20 inFIG. 4 and FIG. 6 in placement of reference clock information extractor15 and reference clock generator 16. In addition, synchronizer 17 anddecoding presenter 18 are also illustrated in FIG. 8 .

The TLV packet includes the 8-bit data type, 16-bit data length, and8*N-bit data, as illustrated in aforementioned FIG. 2 . In addition,1-byte header which is not illustrated in FIG. 2 exists before the datatype, as described above. Here, the data type is specificallyprescribed, for example, as 0x01: IPv4 packet, 0x03: header-compressedIP packet, etc.

In order to store new data in the TLV packet, an undefined area of thedata type is used to prescribe the data type. In order to indicate thatthe reference clock information is stored in the TLV packet, the datatype describes that the data is the reference clock information.

Note that the data type may be prescribed for each kind of the referenceclock. For example, the data types that indicate the short-format NTP,long-format NTP, and PCR (Program Clock Reference) may be prescribedindividually. FIG. 9 is a diagram illustrating an example in which thelong-format NTP is stored in the TLV packet. The long-format NTP isstored in a data field.

In this case, reference clock information extractor 15 analyzes the datatype of TLV packet. When the reference clock information is stored,reference clock information extractor 15 analyzes the data length, andextracts the reference clock information from the data field.

Here, when the data length is uniquely determined by the data type,reference clock information extractor 15 may acquire the reference clockinformation without analyzing a data length field. For example, when thedata type indicates a 64-bit long-format NTP, reference clockinformation extractor 15 may extract a section from (4 bytes+1 bit)-thbit to (4 bytes+64 bits)-th bit. Also, reference clock informationextractor 15 may extract a desired bit from 64-bit data.

Next, the operation flow of reception apparatus 20 when the referenceclock information is stored in the TLV packet (acquisition flow of thereference clock information) will be described with reference to FIG. 10. FIG. 10 is a diagram illustrating the acquisition flow of thereference clock information performed by reception apparatus 20 when thereference clock information is stored in the TLV packet.

In the flow of FIG. 10 , first, decoder 11 decodes the transfer channelcoded data received by receiver 10 (S121), and extracts the TLV packetfrom the transfer slot (S122).

Next, TLV demultiplexer 12 analyzes the data type of TLV packet (S123),and determines whether the data type is the reference clock information(S124). When the data type is the reference clock (Yes in S124),reference clock information extractor 15 extracts the reference clockinformation from the data field of the TLV packet (S125). Then,reference clock generator 16 generates the system clock based on thereference clock information (S126). On the other hand, when the datatype is not the reference clock information, (No in S124), theacquisition flow of the reference clock information ends.

In addition, in an unillustrated flow, IP demultiplexer 13 extracts theIP packet according to the data type. Then, the IP DEMUX process and MMTDEMUX process are performed on the extracted IP packet, and the MMTpacket is extracted. Furthermore, synchronizer 17 outputs video data todecoding presenter 18 with timing with which the time stamp of the videodata contained in the extracted MMT packet coincides with the referenceclock generated in step S126. Decoding presenter 18 decodes and presentsthe video data.

In a transmission method described above, the type data of the TLVpacket indicates a storage place of the reference clock information, andthe reference clock information is stored in the data field of the TLVpacket. Thus, by storing and transmitting the reference clockinformation by the transmission apparatus by using a lower layer orlower protocol than the MMT layer, reception apparatus 20 can reduce theprocesses and time until extraction of the reference clock information.

In addition, since reception apparatus 20 can extract and reproduce thereference clock information in a lower layer extending over the IPlayers, reception apparatus 20 may extract the reference clockinformation by hardware implementation. This allows reception apparatus20 to reduce more influence of jitter or the like than extracting thereference clock information by software implementation, and makes itpossible to generate higher-precision reference clock.

Next, other methods for storing the reference clock information will bedescribed.

When the data length is uniquely determined according to the data typein the aforementioned flow of FIG. 10 , the data length field does notneed to be transmitted. Here, when the data length field is nottransmitted, an identifier is stored indicating that the data lengthfield is data that is not transmitted.

Although the reference clock information is stored in the data field ofthe TLV packet according to the description of FIG. 10 , the referenceclock information may be appended immediately before or after the TLVpacket. Also, the reference clock information may be appendedimmediately before or after data to be stored in the TLV packet. Inthese cases, a data type that allows specification of a position wherethe reference clock information is appended is added.

For example, FIG. 11 is a diagram illustrating structure in which thereference clock information is appended immediately before the IP packetheader. In this case, the data type indicates an IP packet withreference clock information. When the data type indicates an IP packetwith reference clock information, reception apparatus 20 (referenceclock information extractor 15) can acquire the reference clockinformation by extracting bits of a previously prescribed predeterminedlength of the reference clock information from a head of the data fieldof the TLV packet.

At this time, the data length may specify the length of data thatincludes the length of the reference clock information, and may specifythe length that does not include the length of the reference clockinformation. When the data length specifies the length of data thatincludes the length of the reference clock information, receptionapparatus 20 (reference clock information extractor 15) acquires data ofa length obtained by subtracting the length of the reference clockinformation from the data length from immediately after the referenceclock information.

When the data length specifies the length of data that does not includethe length of the reference clock information, reception apparatus 20(reference clock information extractor 15) acquires data of the lengthspecified by the data length from immediately after the reference clockinformation.

In addition, FIG. 12 is a diagram illustrating structure in which thereference clock information is appended immediately before the TLVpacket. The data type is a conventional data type. An identifierindicating that the TLV packet is a TLV packet with reference clockinformation is stored, for example, in a slot header of the transferslot or the TMCC control information. FIG. 13 is a diagram illustratingstructure of the transfer slot, and FIG. 14 is a diagram illustratingstructure of the slot header of the transfer slot.

In FIG. 13 , the transfer slot includes a plurality of slots (120 slotsof Slot #1 to Slot #120 in the example of FIG. 13 ). A bit numbercontained in each slot is a fixed bit number uniquely determined basedon a coding rate of error correction. Each slot has a slot header, andone or more TLV packets are stored. Note that, in FIG. 13 , the TLVpacket has a variable-length.

In FIG. 14 , in a head TLV instruction field (16 bits) of the slotheader is stored a value of a position of a head byte in a first TLVpacket within the slot indicated with a number of bytes from a slot headexcept the slot header. Remaining 160 bits of the slot header isundefined.

The transfer slot includes 120 slots per frame as described above, and amodulation scheme is assigned to the slots in 5-slot unit. In addition,up to 16 streams can be transferred within one frame.

Note that the plurality of streams included in one transfer slot has,for example, different pieces of content (or a company that provides thecontent) transferred by the streams. In addition, each stream includesone or more slots, and one slot does not extend over the plurality ofstreams.

When the identifier indicating that the TLV packet is a TLV packet withreference clock information is stored in the slot header, for example,information that allows specification of a position of the TLV packetwith reference clock information, kind of the reference clockinformation, data length, and the like are stored in the slot obtainedby extending (using) an undefined field of the slot header.

Note that all pieces of information including the information thatallows specification of the position of the TLV packet with referenceclock information, kind of the reference clock information, and datalength do not need to be stored in the slot header. The slot only needsto indicate information that allows specification of and reference tothe TLV packet with reference clock information.

For example, when definition is made such that the reference clockinformation is the 64-bit long-format NTP, that only one TLV packet withreference clock information can be stored in one slot, and that the oneTLV packet with reference clock information is always the head TLVpacket, a flag may be stored in the undefined area of the slot header inthe slot. FIG. 15 is a diagram illustrating an example in which the flagis stored in the undefined area of the slot header.

In FIG. 15 , the flag (described as “F” in the diagram) indicatingwhether the reference clock information is contained in the slot isstored in the undefined area of the slot header. With such a flag,reception apparatus 20 may determine that the head TLV packet is a TLVpacket with reference clock information.

In addition, the identifier (information) indicating that the TLV packetis a TLV packet with reference clock information may be stored in theTMCC control information. FIG. 16 is a diagram illustrating structure ofthe TMCC control information under a transfer scheme for advancedbroadband satellite digital broadcast.

The information for specifying and referencing the TLV packet withreference clock information may be stored in extension informationwithin the TMCC control information illustrated in FIG. 16 , and may bestored in another place within the TMCC control information. Forexample, stream classification/relative stream information in the TMCCcontrol information may be used as information for specifying andreferencing the TLV packet with reference clock information. FIG. 17 isa diagram illustrating the stream classification/relative streaminformation in the TMCC control information.

In FIG. 17 , in the stream classification/relative stream information,the stream classification of each of 16 streams is indicated in 8 bits.That is, 1-frame transfer slot can transfer up to 16 (16-classification)streams. For example, the stream classification of an MPEG2-TS(Transport Stream) stream is “00000000”, and the stream classificationof a TLV stream is “00000010”. However, under the current circumstances,the classifications of other streams are unassigned or undefined.

Therefore, when the stream classification of the TLV stream withreference clock is defined, for example, as “00000100” and the relativestream is a TLV stream with a reference clock, “00000100” is stored inthe stream classification/relative stream information in the TMCCcontrol information. Here, in the stream with the stream classificationof “00000100”, the TLV packet containing reference clock information isstored, for example, once per 5-slot unit, which is a slot assignmentunit, or once per frame unit.

Reception apparatus 20 analyzes the stream classification/relativestream information in the TMCC control information. When the streamclassification is “00000100”, reception apparatus 20 acquires the TLVpacket with a reference clock from the slot determined in advance.

Note that a case may be considered where the stream classificationincluding download type TLV packets and the stream classificationincluding stream type TLV packets, such as video and voice, are defined.In such a case, reception apparatus 20 may determine that the referenceclock information is contained in the stream when the streamclassification of the received stream is a stream type TLV packet. Thisis because the reference clock information is not used in reproductionof download type TLV packets.

In addition, when the information for specifying and referencing the TLVpacket with reference clock information is stored in the extensioninformation of the TMCC control information, for example, informationfor each of the 16 relative streams is stored in the extension area ofthe TMCC control information.

In addition, as illustrated in FIG. 18 , an area into which thereference clock information is stored may be newly defined in theundefined field of the slot header. FIG. 18 is a diagram illustrating anexample in which the reference clock information is stored in theundefined field of the slot header.

In addition, the reference clock information may be stored in apreviously determined slot, and information indicating that thereference clock information is contained may be stored within the slotheader. Here, the previously determined slot is, for example, a headslot of the transfer slot (Slot #1 in the example of FIG. 13 ), and thereference clock information stored in the IP packet may be contained inthe head TLV packet within this slot.

Also, when the plurality of streams are contained in the transfer slot,the previously determined slot may be, for example, a head slot of eachstream contained in the transfer slot, and the reference clockinformation stored in the IP packet may be contained in the head TLVpacket within this slot.

In addition, the TMCC control information may store information forspecifying and referencing the slot header containing the referenceclock information. Note that the storage method of the information forspecifying and referencing the slot header containing reference clockinformation in the TMCC control information is similar to theaforementioned storage method of the information for specifying andreferencing the TLV packet with reference clock information, and thusdescription thereof will be omitted.

Reception apparatus 20 analyzes the TMCC control information, and whendetermination is made such that the reference clock information is inthe slot header, reception apparatus 20 extracts the reference clockinformation from the slot header.

In addition, the TMCC control information may store informationindicating that the reference clock information is contained. FIG. 19 isa block diagram illustrating a functional configuration of receptionapparatus 20 when the information indicating that the reference clockinformation is contained within the slot header is stored in the TMCCcontrol information. FIG. 20 is an acquisition flow of the referenceclock information when the information indicating that the referenceclock information is contained in the slot header is stored in the TMCCcontrol information.

In FIG. 19 , when the information indicating that the reference clockinformation is contained within the slot header is stored in the TMCCcontrol information, in reception apparatus 20, reference clockinformation extractor 15 acquires the reference clock signal from thetransfer slot that is output from decoder 11.

In the flow of FIG. 20 , decoder 11 decodes the transfer channel codeddata (S131), analyzes the TMCC control information (S132), anddetermines whether the reference clock information is in the slot headerwithin the transfer slot (S133). When the reference clock information isin the slot header (Yes in S133), reference clock information extractor15 extracts the reference clock information from the slot header (S134),and reference clock generator 16 generates the reference clock of thesystem (system clock) based on the reference clock information (S135).On the other hand, when the reference clock information is not in theslot header (No in S133), the acquisition flow of the reference clockinformation ends.

Such reception apparatus 20, which can acquire the reference clockinformation in the layer of the transfer slot, can acquire the referenceclock information more quickly than a case where the reference clockinformation is stored in the TLV packet.

As described above, by storing the reference clock information in theTLV packet or transfer slot, reception apparatus 20 can reduce theprocesses until the acquisition of the reference clock information, andcan shorten acquisition time of the reference clock information.

In addition, by storing the reference clock information in a physicallayer, reception apparatus 20 can easily implement acquisition andreproduction of the reference clock information by hardware, and clockreproduction with high-precision is possible compared to the case ofacquisition and reproduction of the reference clock information bysoftware.

In addition, in the aforementioned transmission method according to thefirst exemplary embodiment, in a system in which a plurality of layers(protocols) exists including the IP layer, the transmission apparatusadds the time stamp of a medium based on the reference clock informationin the layers upper than the IP layer, and transmits the reference clockinformation in the layers lower than the IP layer. This allows receptionapparatus 20 to easily process the reference clock information byhardware.

Based on a similar idea, the reference clock information may be storedin a condition of not being stored in the MMT packet within the IPpacket. Even in such a case, reception apparatus 20 can reduce theprocesses for acquiring the reference clock information as compared withthe case where the reference clock information is stored in the MMTpacket.

[Transmission Cycle of the Reference Clock Information]

A transmission cycle of the reference clock information will besupplemented below.

In the case of storing the reference clock information in the TLVpacket, for example, the transmission apparatus stores time when a headbit of the TLV packet is transmitted as the reference clock information.In addition, not the transmission time of the head bit but predeterminedtime determined differently may be stored as the reference clockinformation.

The TLV packet that contains the reference clock information istransmitted at predetermined intervals. In other words, the TLV packetthat contains the reference clock information is contained in thetransfer slot and is transmitted in a predetermined transmission cycle.For example, at least one or more pieces of the reference clockinformation may be stored in the TLV packets for transfer at intervalsof 100 ms.

In addition, the transmission apparatus may place the TLV packets thatcontain the reference clock information at predetermined intervals atpredetermined positions of the transfer slot under the advanced BStransfer scheme. In addition, the transmission apparatus may store theTLV packet containing the reference clock information once every 5-slotunit, which is a slot assignment unit of the TLV packet, and may storethe reference clock information in the head TLV packet of the first slotof the 5-slot unit. That is, the transmission apparatus may place theTLV packet that contains the reference clock information at a headwithin the head slot within the transfer slot (that is, immediatelyafter the slot header).

In addition, the transmission apparatus may place the TLV packets thatcontain the reference clock information at predetermined intervals atpredetermined positions of the transfer slot under the transfer schemeof the advanced broadband satellite digital broadcasting. For example,the transmission apparatus may store the reference clock informationonce every 5-slot unit, which is a slot assignment unit, in the head TLVpacket of the first slot. That is, the TLV packet positioned at a headwithin the head slot of each stream contained in the transfer slot maycontain the reference clock information. In addition, the referenceclock information may be stored in the first slot within the relativestream.

In addition, the transmission cycle and transmission interval of thereference clock information may be changed according to a modulationscheme or coding rate of the transfer channel coding scheme.

[Method for Acquiring the Reference Clock Information in the Upper LayerQuickly]

Next, a method will be described for shorten time to the acquisition ofthe reference clock information by reception apparatus 20 performingbatch DEMUX processing from the lower layer to the upper layer.

Here, a method will be described by which the transmission apparatusstores the reference clock information in the upper layer such as theMMT packet, and stores in the IP packet the MMT packet in which thereference clock information is stored. In the method described below, bydefining a protocol for storing in the TLV packet the IP packet in whichthe reference clock information is stored, the reception apparatus makesa direct reference to the MMT packet, which is the upper layer, from thelower layer such as the TLV packet, and acquires the reference clockinformation contained in the MMT packet without performing normal DEMUXprocessing.

The transmission apparatus contains the reference clock information inthe aforementioned control information stored in the MMT packet. Thepreviously determined packet ID is added to the control informationcontaining the reference clock information. Then, the transmissionapparatus stores the MMT packet that contains the reference clockinformation in a dedicated IP data flow, and adds the previouslydetermined source IP address, destination IP address, source portnumber, destination port number, and protocol classification.

On receipt of the generated transfer channel coded data, receptionapparatus 20 can extract the IP packet that contains the reference clockinformation by TLV demultiplexer 12 acquiring the previously determinedIP data flow.

Note that, when the IP packet undergoes header compression processing,the reception apparatus adds, for example, an identifier indicating thatthe IP packet contains the reference clock information to a contextidentifier that indicates identical IP data flow. The context identifieris stored in a compressed IP packet header. In this case, receptionapparatus 20 can extract the IP packet that contains the reference clockinformation with reference to the context identifier in the compressedIP packet header.

In addition, the IP packet containing the reference clock informationmay be prescribed not to undergo the header compression, and may beprescribed to always undergo the header compression. It may beprescribed that the previously determined context identifier is added tothe IP packet containing the reference clock information, and that allthe headers are compressed.

In addition, such a method is also possible that a TLV data type fielddefines an identifier indicating that the TLV packet is an IP packetthat belongs to the IP data flow containing the reference clockinformation, or an identifier indicating that the TLV packet is acompressed IP packet that belongs to the IP data flow containing thereference clock information. Also, such an identifier may be defined ina field other than the TLV data type field.

When a direct reference to the reference clock information is made fromthe lower layer, the reference clock information is stored at apreviously determined position, and packets in which the reference clockinformation is stored (such as the MMT packet, IP packet, and TLVpacket) are packets dedicated to the reference clock information. Inaddition, a length of the field before the reference clock informationis fixed by a packet header length being fixed.

However, the length of the field before the reference clock informationdoes not need to not be fixed. The reception apparatus only needs tospecify the length of the field before the reference clock informationin the lower layer. For example, when information on the length to thereference clock information includes two types, A and B, receptionapparatus 20 can specify the position of the reference clock informationby signaling which of A and B the length information is in the lowerlayer. Alternatively, by the transmission apparatus storing, in thelower layer, positional information on the reference clock informationthat allows a direct reference to the reference clock information in theupper layer, reception apparatus 20 may make a reference from the lowerlayer based on the positional information.

The following specifically describes a method for shortening acquisitiontime of the reference clock information in the upper layer.

Reception apparatus 20 determines the TLV data type. On determinationthat the reference clock information is contained, reception apparatus20 acquires the reference clock information contained within the MMTpacket directly from the IP packet.

Reception apparatus 20 may extract the reference clock informationcontained in the MMT packet by extracting a bit string at a specificposition from the IP packet or compressed IP packet, with analysis ofthe IP address, port number, or context identifier omitted. “Extractinga bit string at a specific position” means, for example, extractinginformation of a specific length from a position that is offset byfixed-length bytes from the TLV packet header. Reception apparatus 20acquires the reference clock information by “extracting a bit string ata specific position”.

The offset length of the fixed-length bytes for extracting the referenceclock information is uniquely determined for each of the IP packet andthe compressed IP packet. Therefore, reception apparatus 20 can acquirethe reference clock information by extracting the information of thespecific length from the position that is offset by the fixed-lengthbytes immediately after determining the TLV data type. Note that theextraction of the information may be performed not from the positionthat is offset by the fixed length from the TLV packet header but from aposition that is offset by the fixed length from a specific field ofTLV.

Note that the aforementioned method is one example, and the referenceclock information in the upper layer may be acquired from the lowerlayer through definition of another protocol or identifier. For example,an identifier indicating whether the IP packet contains the referenceclock information may be stored in a field other than the TLV data typefield.

In addition, for example, reception apparatus 20 may extract referencetime information contained in the MMT packet by extracting the bitstring at a specific position from the IP packet or compressed IPpacket, with analysis of the IP address, port number, or contextidentifier omitted.

When it is difficult to determine the IP data flow that contains thereference clock information from identification information on the IPdata flow, reception apparatus 20 may specify the MMT packet thatcontains the reference clock information based on unique identificationinformation (packet ID) added to the MMT packet that contains thereference clock information. In this case, the reference clockinformation is extracted from the specific field as described above.

In addition, when the reference clock information contained in the MMTpacket is not stored at a position determined in advance or when theposition where the reference clock information contained in the MMTpacket is stored cannot be specified, reception apparatus 20 specifiesthe MMT packet that contains the reference clock information by usingthe aforementioned method, specifies the position of the reference clockinformation based on MMT packet header information, and extracts thereference clock information.

Note that, although an example has been described above in which the MMTpacket is stored in the IP packet, data to be stored in the IP packetdoes not need to be the MMT packet, but may be, for example, data thathas another data structure. That is, the reference clock information maybe contained in the IP packet in data structure different from datastructure of the MMT packet. Even for the data in different datastructure, in a similar manner to the aforementioned example, datacontaining the reference clock information is stored in a dedicated IPdata flow, and identification information indicating that the datacontains the reference clock information and identification informationindicating that the data is an IP data flow containing the referenceclock information are added.

Reception apparatus 20 identifies that the data is data containing thereference clock information, or that the data is an IP data flowcontaining data containing the reference clock information. When thereference clock information is contained, reception apparatus 20extracts the reference clock information. In addition, when thereference clock information is stored at a specific position of data,reception apparatus 20 can extract the reference clock informationcontained in the data with reference to the specific position frompacket structure of the lower layer.

In the aforementioned example, in order to extract the reference clockinformation from the IP packet or the compressed IP packet, based onwhether the data is the IP packet or the compressed IP packet, receptionapparatus 20 extracts the reference clock information from fixed-lengthoffset positions different from each other. However, if it ispredetermined that header compression processing is omitted on the IPpacket that contains the reference clock information, or if it ispredetermined that all the IP packets that contain the reference clockinformation undergo header compression, reception apparatus 20 may omitthe determination on whether the data is the IP packet or the compressedIP packet. In addition, reception apparatus 20 may perform determinationon whether the reference clock information is contained, after theheader of the compressed IP packet is decompressed.

A reception method for extracting the bit string at a specific positionfrom the IP packet or compressed IP packet will be described below withreference to the flowchart. FIG. 21 is a flowchart for extracting thebit string at a specific position from the IP packet or compressed IPpacket. Note that the configuration of reception apparatus 20 is similarto the block diagram illustrated in FIG. 8 .

In the flow of FIG. 21 , first, decoder 11 decodes the transfer channelcoded data received by receiver 10 (S141), and extracts the TLV packetfrom the transfer channel slot (S142).

Next, TLV demultiplexer 12 analyzes the data type of TLV packet (S143),and determines whether the data type is an IP that contains referenceclock information (S144). When the determination is made such that thedata type is not an IP packet that contains reference clock information(No in S144), the flow ends. When the determination is made such thatthe data type is an IP packet that contains reference clock information(Yes in S144), TLV demultiplexer 12 determines whether the IP header iscompressed (S145).

When the IP header is not compressed (No in S145), reference clockinformation extractor 15 acquires the reference clock informationcontained within the MMT packet at a position that is offset byfixed-length N bytes from the TLV header (S146). When the IP header iscompressed (Yes in S145), reference clock information extractor 15acquires the reference clock information contained within the MMT packetat a position that is offset by fixed-length M bytes from the TLV header(S147).

For example, when the determination is made in step S145 such that theIP header undergoes compression processing, in step S146, referenceclock information extractor 15 acquires the reference clock informationcontained in the MMT packet from the position that is offset by N bytesfrom the TLV header. On the other hand, when the determination is madein step S145 such that the IP header does not undergo compressionprocessing, in step S147, reference clock information extractor 15acquires the reference clock information contained in the MMT packetfrom the position that is offset by M bytes from the TLV header.

Finally, reference clock generator 16 generates the system clock basedon the reference clock information (S148).

Note that, since data structure of the IP packet header differsaccording to whether the IP packet is IPv4 or IPv6, the fixed-length Nbytes and M bytes have different values.

While the normal MMT packet containing voice, video, control signal, andthe like undergoes DEMUX processing in normal steps, the MMT packetcontaining the reference clock information undergoes batch DEMUXprocessing from the lower layer to the upper layer. This allows thereception apparatus to acquire the reference clock information in thelower layer even when the reference clock information is stored in theupper layer. That is, the reception apparatus can reduce the processesfor acquisition of the reference clock information, shorten time to theacquisition of the reference clock information, and facilitate hardwareimplementation.

SECOND EXEMPLARY EMBODIMENT

Currently, as a method for using an extension area in TMCC controlinformation (hereinafter also simply referred to as TMCC) under anadvanced BS transfer scheme, ARIB (Association of Radio Industries andBusinesses) is studying a method for transmitting urgent information andthe like as a payload.

However, a proposed conventional method for using the extension area inthe TMCC control information is limited to a method for transmitting adata payload, such as text and images, by using the TMCC controlinformation extending over several frames. Therefore, the method forusing the extension area in the TMCC control information will belimited, which needs to be addressed.

For example, it is difficult to store control information (controlsignal) that does not change in value for each frame, such as aconventional transfer mode and slot information, or control informationthat changes in value for each frame, such as reference clockinformation, in the extension area of the TMCC control informationsimultaneously with payload data extending over several frames.

Therefore, the second exemplary embodiment describes a method for makingit possible to store data with different reception processingsimultaneously in the extension area of the TMCC control information, bydividing the extension area of the TMCC control information inaccordance with a classification of information and data to be stored inthe extension area of the TMCC control information. The presentdisclosure can enhance flexibility of extension by providingextensibility to the use of the extension area. In addition, thereception apparatus can perform reception and analysis of the TMCCcontrol information by reception methods different for eachclassification based on the classification of data.

In addition, the method according to the present disclosure allowspayload data extending over several frames and payload data of one frameto be included together in the extension area. Since the receptionapparatus can acquire the payload data of one frame first even while thepayload data extending over several frames cannot be received, urgentinformation can be acquired and presented more quickly.

[Structure of TMCC Extension Information]

Structure of TMCC extension information will be described below. Notethat basic structure of the TMCC control information is structureillustrated in FIG. 16 . The control information to be stored in theTMCC control information is classified roughly into a first type and asecond type below.

The first type of control information relates to frames, and does notchange in value for each frame. A minimum update interval of the controlinformation that does not change in value for each frame is a frameunit. Here, when the value of the control information is changed, thecontrol information after the change is transmitted two frames ahead. Inaddition, when the value of the control information is changed,notification is made by increment of an 8-bit change instruction.Specifically, information other than pointer information and slotinformation corresponds to the control information that does not changein value for each frame.

The second type of control information relates to frames, and changes invalue for each frame. Since the control information that changes invalue for each frame is information that changes in value for eachframe, the change instruction is not made. Specifically, such controlinformation is the pointer information and the slot information.

FIG. 22 is a diagram illustrating an example of structure of the TMCCextension information. FIG. 22B is a diagram illustrating anotherexample of structures of TMCC extension information. In FIG. 22A, theTMCC extension information includes 16-bit extension identification and3598-bit extension area. Setting a value other than all 0 in theextension identification validates the extension area.

FIG. 22B is a diagram illustrating an example of a conventionallyproposed bit assignment method when the extension area is used as apayload. In FIG. 22B, when the extension area is used as a payload, anumber of pages includes 16 bits, and indicates over how many frames ofthe TMCC control information during transfer an additional informationpayload is transferred.

A page number includes 16 bits, and indicates in which page the TMCCcontrol information during transfer is among the number of pages. Anadditional information classification includes 8 bits, and specifies theclassification of the additional information. Specifically, theadditional information classification is, for example, superimposedcharacters (subtitles), graphics, voice, and the like.

All of the extension area will be used as a payload, and thus it isdifficult to store control information such as the conventional TMCCcontrol information.

[Extension Method of the TMCC Extension Area]

Here, a method will be described for storing data with differentreception processing in the TMCC extension area, by dividing the TMCCextension area in accordance with the classification of information anddata to be stored in the TMCC extension area.

The classification of information and data to be stored in the TMCCextension area (hereinafter referred to as an extension classification)is classified as follows, for example.

Type A:

-   -   Type A indicates control information that relates to frames, and        does not change in value for each frame.    -   The minimum update interval is a frame unit. When there is a        change in value, information after the change is transmitted two        frames ahead.    -   In addition, when there is a change in value, notification of        the change is made by increment of the 8-bit change instruction.        Type B:    -   Type B indicates control information that relates to frames, and        changes in value for each frame.    -   Type B indicates information that changes in value for each        frame, and the change instruction is not made.        Type C:    -   Type C indicates information or data that is used as a payload        (conventional extension scheme).    -   However, for the change instruction, a change instruction field        which is identical to TMCC which is not the extension area may        be used, and the change instruction field may be independently        prescribed in the extension area.

FIG. 23 is a diagram illustrating an example of data structure (bitarrangement) of the extension area where the classified extensionclassification is used. FIG. 24A is a diagram illustrating an example ofsyntax when the extension classification is used. FIG. 24B is a diagramillustrating another example of syntax when the extension classificationis used.

In FIG. 23 , the aforementioned three types are defined as the extensionclassification. In addition, in FIG. 24A, subsequent to storage of adata length in each of the three types of extension classification,extension data with a length indicated in the data length is stored foreach extension classification. The reception apparatus extracts datawith the length indicated in the data length from the extension area foreach extension classification, and performs processing.

For example, regarding data of Type A, the reception apparatus acquiresthe data when there is a change instruction. When there is a change inthe data of Type A, the reception apparatus considers that the controlinformation is changed, and performs processing on the controlinformation in accordance with the change.

In addition, regarding data of Type B, since the data of Type B changesin value for each frame, the reception apparatus acquires the data forevery frame. For example, when the reference clock information thatchanges in value for each frame is stored in the TMCC controlinformation, the reference clock information is stored in a data area ofType B.

Data of Type C contains payload information of the conventionalextension scheme. Regarding the data of Type C, the reception apparatusperforms operation in accordance with acquisition under the conventionalextension scheme.

In the aforementioned example, details of data structure for eachextension classification are separately prescribed. When prescribedseparately, an identifier similar to the additional informationclassification and an object service specification method in the data ofType C in FIG. 22B may be prescribed in other types. Note that theadditional information classification may be defined using a commontable, and the extension identification and the additional informationclassification may be merged.

In addition, information that may change in data length on the way maybe considered as a classification similar to the data of Type A. Whenthere is a change in data length, a change instruction may be madethrough transmission of information after the change two frames ahead.When there is a change instruction, the reception apparatus confirmswhether there is any change in the data length with reference to thedata length of the extension classification.

Note that the data structure is not limited to the structure asillustrated in FIG. 23 . For example, when the data length of theextension classification is fixed in advance, transmission of the datalength may be omitted. Specifically, when the data length with theextension classification of Type A is fixed-length in FIG. 23 ,placement of the data length with the extension classification of Type Amay be omitted within the data structure. In addition, when the datalength with the extension classification of Type A and the data lengthwith the extension classification of Type B are fixed-length, placementof the data length of all types may be omitted. In addition, a flag thatindicates whether there is any data of the extension classification maybe provided within the data structure.

In addition, syntax for using the extension classification is notlimited to syntax illustrated in FIG. 24A. For example, in FIG. 24B, anextension area number is set, and the extension classification andextension area length are stored for each extension area number in thesyntax. Subsequently, the extension data of the extension area number isstored in the syntax.

The syntax in FIG. 24A and FIG. 24B supports addition of the extensionclassification in the future. In addition, since the syntax in FIG. 24and FIG. 24B enables storage of a plurality of pieces of data withidentical extension classification, it is not necessary to determinedetails of data structure for each identical extension classification inadvance. In addition, even when used as a payload (as Type C), thesyntax in FIG. 24 and FIG. 24B allows description of a plurality ofpieces of data with different number of pages, such as video and voice,in an identical frame.

Note that, in the syntax of FIG. 24B, the extension area number,extension classification, and extension area length may beclassifications similar to Type A. That is, these pieces of informationmay be prescribed to be information that follows the change instruction.Therefore, the reception apparatus can easily make a determination ofpresence of changes by continuous storage of data that follows thechange instruction.

In addition, an undefined area may be provided in the extensionclassification in preparation for future extension. As an extensionclassification to be introduced in the future, for example, thefollowing classifications are assumed.

-   -   This is a control signal to be updated for each several frames,        and the change instruction is not made.    -   For an urgent signal, the change instruction is made in a        similar manner to Type A. However, processing of value change is        performed in the frame after acquisition of the change        instruction, instead of after acquisition of information that is        two frames ahead.

In addition, for the aforementioned urgent signal, an urgent flag may betransmitted using the extension classification accompanied by the changeinstruction, and urgent data may be transmitted using a payload. Inaddition, the extension classification may be classified in accordancewith whether to follow the change instruction.

[Detailed Configuration and Operation Flow]

A functional configuration and operation flow of the reception apparatusas described above will be described. FIG. 25 is a block diagramillustrating the functional configuration of the reception apparatusaccording to the second exemplary embodiment. FIG. 26 is a diagramillustrating the operation flow of the reception apparatus according tothe second exemplary embodiment. Note that, in the followingdescription, the extension classification includes three types, Type A,Type B, and Type C, as described above.

As illustrated in FIG. 25 , reception apparatus 40 includes extensionidentifier 41, extension classification determiner 42, changeinstruction checker 43, data update checker 44, and update data acquirer45.

First, extension identifier 41 analyzes the extension identification ofthe TMCC control information (S161). When the extension identificationis other than all 0 here, extension identifier 41 determines that theextension area is effective, and reception apparatus 40 executes thefollowing processing for each extension area.

Next, extension classification determiner 42 discriminates (determines)the extension classification (S162). When it is discriminated that theextension classification is Type A (Type A in S162), data of an areaspecified by the extension area length is control information which doesnot change in value for each frame, the control information followingthe change instruction. Therefore, change instruction checker 43 checksthe change instruction for each frame (S163).

Subsequently, data update checker 44 determines data update (S164). Whenit is determined that there is a change instruction and that there is achange in the extension data (Yes in S164), update data acquirer 45acquires updated extension data and executes processing accompanying thechange (S165).

On the other hand, when it is not determined as described above in stepS164 (No in S164), update data acquirer 45 determines that there is nochange in the extension data.

In addition, when it is discriminated in step S162 that the extensionclassification is Type B (Type B in S162), update data acquirer 45references data specified by the extension area length, acquires dataupdated for each frame, and executes processing accompanying the change(S167).

When it is discriminated in step S162 that the extension classificationis Type C (Type C in S162), update data acquirer 45 executes processingbased on the conventional reception method under the payload extensionscheme (S166).

Note that, when it is discriminated that the extension area number,extension classification, and extension area length are classificationssimilar to Type A that follows the change instruction as describedabove, update data acquirer 45 checks change instructions. When there isa change instruction, update data acquirer 45 checks whether informationis updated.

Note that reception apparatus 40 may determine reception processingbased on the extension classification, and may determine in whichprocessing block the data processing should be performed. Receptionapparatus 40 may determine, for example, to process the data of Type Aand the data of Type B by hardware, and to process the data of Type C bysoftware.

Advantageous Effects, Etc.

As described above, the second exemplary embodiment has described themethod for dividing the TMCC extension area under the advanced BStransfer scheme for each extension classification, and for storing theextension data in the TMCC extension area. Reception apparatus 40determines the extension data processing method based on the extensionclassification.

Accordingly, the TMCC extension area can store a plurality of pieces ofdata with different reception processing simultaneously. That is, thepresent disclosure makes it possible to provide extensibility to themethod for using the TMCC extension area.

Specifically, for example, the TMCC extension area can store the payloadand the reference clock information simultaneously.

In addition, it is possible to cause the payload data extending overseveral frames and the payload data of one frame to be included togetherin the TMCC extension area. Accordingly, even when it is difficult toreceive the payload data extending over several frames, receptionapparatus 40 can first acquire the payload data of one frame. Therefore,reception apparatus 40 can acquire and present urgent information morequickly.

THIRD EXEMPLARY EMBODIMENT

A third exemplary embodiment describes a method for transmitting aplurality of pieces of reference clock information that belong todifferent layers.

SUMMARY

FIG. 27 is a diagram schematically illustrating an example in which thepieces of reference clock information are stored in the respectiveplurality of layers.

In FIG. 27 , a first layer is a layer upper than a second layer, and thefirst layer stores first reference clock information. The second layerstores second reference clock information.

A transmission apparatus performs MUX processing in the second layerafter performing MUX processing in the first layer. In addition, areception apparatus performs DEMUX processing in the first layer afterperforming DEMUX processing in the second layer.

When storing the first reference clock information in the first layerand storing the second reference clock information in the second layer,as information that indicates a relationship between the first referenceclock information and the second reference clock information, thetransmission apparatus stores, for example, the following information.

As a first example, the transmission apparatus allows a transmissionsignal (for example, a transfer frame) to include information indicatingthat the plurality of pieces of reference clock information is storedwithin the transmission signal.

Specifically, in at least one or more layers among the layers in whichthe reference clock information is contained, the transmission apparatusstores information indicating that the reference clock information isstored also in layers other than the aforementioned layers.

In addition, in a layer in which the reference clock information is notcontained, the transmission apparatus may indicate that the plurality ofpieces of reference clock information is stored. For example, thetransmission apparatus may store, in the lower layer (second layer),information that indicates whether the reference clock information iscontained in the upper layer (first layer). The reception apparatus maydetermine whether to perform acquisition of the reference clockinformation and reproduction of a reference clock in the lower layer inprocessing of the lower layer taking into consideration whether thereference clock information is contained in the upper layer.

As a second example, the transmission apparatus allows the transmissionsignal to include information regarding the first reference clockinformation and the second reference clock information.

Specifically, the transmission apparatus stores, in each layer,information that indicates a type of reference clock informationcontained in the layer. Alternatively, the transmission apparatusstores, in each layer, information that indicates a type of referenceclock information contained in a layer other than the aforementionedlayer.

The reference clock information is, for example, a plurality of types ofinformation, such as 32-bit NTP, 64-bit NTP, and 24-bit SMPTE (Societyof Motion Picture and Television Engineers) time code. The informationthat indicates the type of reference clock information is informationthat can specify a format (including information such as precision) ofthe reference clock information.

Note that, when it is known in advance that a predetermined type ofreference clock information is contained, the layer does not need tocontain the information that indicates the type of reference clockinformation.

As a third example, the transmission apparatus allows the transmissionsignal to include information that indicates a relative relationshipbetween the first reference clock information and the second referenceclock information.

Specifically, the transmission apparatus allows the transmission signalto include information that indicates a relative relationship ofprecision of the reference clock information. For example, thetransmission apparatus allows the transmission signal to includeinformation that indicates whether precision of the second referenceclock information is high or low with respect to precision of the firstreference clock information.

In addition, the information that indicates the relative relationshipmay be information that indicates the relative relationship based onsize of a total bit number of the reference clock information, and maybe information that indicates the relative relationship of a dynamicrange based on size of a bit number of an integer part.

Alternatively, the information that indicates the relative relationshipmay be information that indicates the relative relationship of precisionof resolving power (resolution) based on size of a bit number of adecimal part. In addition, the information that indicates the relativerelationship may be information that indicates the relative relationshipof precision at a time of acquisition of the reference clockinformation, based on a difference in precision resulting from adifference in reliability of the reference clock information in thetransmission apparatus, quality of a transfer channel, and throughput intransmission processing and reception processing.

In addition, the information that indicates the relative relationshipmay be information that indicates a difference in precision between thepieces of reference clock information. For example, when there is adifference in the decimal bit number, the information that indicates therelative relationship may be information that indicates the differencein the decimal bit number. The information that indicates the relativerelationship may be information that indicates information thatindicates whether the precision differs for each. When the precisiondiffers for each, the information that indicates the relativerelationship may be stored. Note that, when the relative relationship ofprecision is known in advance, the information that indicates therelative relationship of precision does not need to be included.

By the transmission apparatus transmitting the information thatindicates the relative relationship of precision, when the transmittedinformation indicates that precision of the second reference clockinformation is low with respect to precision of the first referenceclock information, the reception apparatus can perform control includingavoiding performing acquisition and reproduction of the second referenceclock information, performing acquisition and reproduction of the firstreference clock information, and performing synchronous reproductionbased on the first reference clock information. Alternatively, when thetransmitted information indicates that precision of the second referenceclock information is high with respect to precision of the firstreference clock information, the reception apparatus can perform controlincluding avoiding performing acquisition and reproduction of the firstreference clock information, performing acquisition and reproduction ofthe second reference clock information, and performing synchronousreproduction based on the second reference clock information.

As a fourth example, the transmission apparatus allows the transmissionsignal to include information that indicates a relative relationship oftime between the pieces of reference clock information. Specifically,the transmission apparatus transmits information that indicates relativetime between the first reference clock information and the secondreference clock information. For example, the transmission apparatustransmits the information that indicates relative time by usingCRI_descriptor in an MMT scheme. Note that information that indicateswhether the first reference clock information and the second referenceclock information are generated based on an identical reference clockmay be included in the transmission signal.

When each of the pieces of reference clock information is generatedbased on an identical reference clock, in the reception apparatus, adifference may arise in acquisition timing between the first referenceclock information and the second reference clock information. That is, afixed time difference arises between End-to-End delays of respectivepieces of reference clock information.

Therefore, the transmission apparatus calculates a time difference Δ_Abetween imparting timing of the first reference clock information andimparting timing of the second reference clock information, and storesthe calculated time difference Δ_A in the transmission signal as timecorresponding to acquisition timing of the first reference clockinformation and the second reference clock information. The receptionapparatus acquires the time difference Δ_A from the transmission signal,and corrects the End-to-End delay difference between the first referenceclock information and the second reference clock information based onthe time difference Δ_A.

In addition, when each piece of the first reference clock informationand the second reference clock information is generated based on thereference clock of an identical format and when each piece of the firstreference clock information and the second reference clock informationhas a fixed delay difference Δ_B, the transmission apparatus stores andtransmits information that indicates the fixed delay difference Δ_B ofthe reference clock information. The reception apparatus acquires thedelay difference Δ_B, and corrects the fixed delay difference of thereference clock based on the delay difference Δ_B.

In addition, when the reference clock on which each piece of the firstreference clock information and the second reference clock informationis based has the fixed delay Δ_B, the transmission apparatus transmits atransmission signal that includes the fixed delay Δ_B in the secondlayer, which is a lower layer.

In addition, when each piece of the first reference clock informationand the second reference clock information is generated based on thereference clock of an identical format, the second reference clockinformation may be represented with a difference from the firstreference clock information based on the first reference clockinformation. Note that the first reference clock information may berepresented with a difference from the second reference clockinformation based on the second reference clock information.

As a fifth example, when the plurality of pieces of reference clockinformation is stored, the transmission apparatus allows thetransmission signal to include information on whether to use thereference clock information stored in a different layer. Thetransmission apparatus allows the transmission signal to include, forexample, information as to instructions to use, in the first layer, thesecond reference clock information stored in the second layer. Based onthe information included in the transmission signal, the receptionapparatus can generate the second reference clock information and outputthe generated second reference clock information in the first layer.

The information described above is stored in at least one or morelayers. For example, regarding the information described above, theabove-described information may be stored in the first layer among theplurality of layers, may be stored in the second layer, and may bestored in the first layer and the second layer. In addition, regardingthe information described above, in each layer, information regardingthe reference clock information in the layer may be stored, andinformation that indicates the relative relationship may be stored in atleast one or more layers.

Note that the information that indicates the relative relationship ispreferably stored in the lower layer (second layer). In addition, theinformation that indicates the relative relationship may be stored in alayer lower than the second layer (not illustrated in FIG. 27 ). Thereception apparatus, which can acquire information regarding thereference clock information in the upper layer (first layer) whenperforming DEMUX processing in the lower layer (second layer), canperform higher-speed processing.

Note that a combination of the first layer and the second layer may beany combination. For example, the combination of the first layer and thesecond layer may be a combination of an MMT layer and an IP layer, acombination of an MMT layer and a transfer layer, and a combination ofan IP layer and a transfer layer. In addition, for MMToverTS, thecombination of the first layer and the second layer may be a combinationof MMT and TS.

In addition, the information described above is stored in a controlsignal of each layer. For example, under the MMT scheme, the informationdescribed above is stored in a descriptor, table, message, or packetheader information. Under an MPEG2-TS scheme, the information describedabove is stored in a descriptor, table, section, or header information.In addition, the information described above may be stored in TMCC or aslot header in the transfer layer. When a transfer scheme is DVB(Digital Video Broadcasting), the information described above is storedin TPS (Transmission Parameters Signaling), L1 data, L2 data, P1 data,P2 data, and the like.

Note that the first reference clock information and the second referenceclock information may be pieces of reference clock information of anidentical type, and may be pieces of reference clock information ofdifferent types. In addition, the first reference clock information andthe second reference clock information may be pieces of reference clockinformation with different precision. The first reference clockinformation and the second reference clock information may be pieces ofreference clock information based on an identical reference clock, andmay be pieces of reference clock information based on differentreference clocks.

In addition, the transmission apparatus may transmit three or morepieces of reference clock information, and may store the three or morepieces of reference clock information in three or more respective layersfor transmission. In addition, the transmission apparatus may store therespective pieces of reference clock information in different fieldswithin data structure in an identical layer. In addition, another layermay exist between the first layer and the second layer.

The reference clock information, which is, for example, NTP, time code,and PTP (Precision Time Protocol), may be reference clock informationother than these examples. In addition, the reference clock informationmay be another piece of information regarding time (for example, TOT(Time Offset Table) and TDT (Time Date Table)).

FIG. 28 is a diagram schematically illustrating an example in which aplurality of pieces of reference clock information is stored in onelayer. In FIG. 28 , the first layer contains three pieces of referenceclock information, that is, first reference clock information, secondreference clock information, and third reference clock information.

The transmission apparatus may store information regarding the firstreference clock information and the second reference clock information,information that indicates a relative relationship (of precision ortime) between the first reference clock information and the secondreference clock information, and the like.

As one example, a case will be described of storing a plurality ofpieces of reference clock information in TMCC. As described in FIG. 17 ,a broadcasting station apparatus can transmit 16 streams under anadvanced BS transfer scheme, and it is assumed that, for example, piecesof data generated by different broadcasting station apparatuses arestored in separate streams. FIG. 29 is a block diagram for describing anexample in which the pieces of data generated by different broadcastingstation apparatuses are stored in separate streams.

In FIG. 29 , each of first broadcasting station apparatus 51, secondbroadcasting station apparatus 52, and third broadcasting stationapparatus 53 transmits data generated in each broadcasting stationapparatus to satellite transmitting station apparatus 54 by usingcables, such as an optical network, and radio. Satellite transmittingstation apparatus 54 multiplexes the streams of respective broadcastingstation apparatuses into an identical transfer channel under theadvanced BS transfer scheme. Satellite transmitting station apparatus 54stores in TMCC the pieces of reference clock information correspondingto the respective streams of the first, second, and third broadcastingstation apparatuses, and transfers the pieces of reference clockinformation to reception apparatus 50.

In FIG. 28 , the first reference clock information corresponds to thereference clock information of first broadcasting station apparatus 51,the second reference clock information corresponds to the referenceclock information of second broadcasting station apparatus 52, and thethird reference clock information corresponds to the reference clockinformation of third broadcasting station apparatus 53.

In a case where each broadcasting station apparatus performs processingbased on common reference clock information, such as NTP, in satellitetransmitting station apparatus 54, the pieces of reference clockinformation in respective broadcasting station apparatuses 51, 52, 53have a time difference due to a difference in the End-to-End delaycaused by a reception processing delay or a transfer delay until arrivalat satellite transmitting station apparatus 54.

When the common reference clock information to be used in respectivebroadcasting station apparatuses 51, 52, 53 is NTP_base, the firstreference clock information in satellite transmitting station apparatus54 is denoted as NTP_base+Δ1, the second reference clock information isdenoted as NTP_base+Δ2, and the third reference clock information isdenoted as NTP_base+Δ3.

FIG. 30 is a diagram for describing a transmission method of pieces ofdifference information. In FIG. 30 , the transmission apparatus(satellite transmitting station apparatus 54) may transmit the commonreference clock information NTP_base, and may transmit the pieces ofdifference information between respective pieces of reference clockinformation and the common reference clock information (Δ1, Δ2, Δ3). Inaddition, for example, out of 64-bit reference clock information, byrepresenting base reference clock information with top 16 bits, andrepresenting the difference information with remaining 48 bits, thetransmission apparatus can reduce an amount of information (size) fortransferring the reference clock information.

Note that the base reference clock information (reference value) doesnot need to be NTP_base, but may be the earliest (with small delay)reference clock information among the plurality of pieces of referenceclock information. Alternatively, the base reference clock information(reference value) may be a value smaller than a value of the earliestreference clock information.

In addition, FIG. 31 is a diagram for describing a variation of thetransmission method of the difference information. In FIG. 31 , the basereference clock information and the difference information may betransmitted at different frequencies; for example, the base referenceclock information is transmitted for every frame, and the differenceinformation is transmitted in order for every three frames. By thetransmission method in FIG. 31 , the transmission apparatus can reducethe amount of information (size) for transferring the reference clockinformation.

Reception apparatus 50 uses the base reference clock information toreproduce the base reference clock. After reproduction of the basereference clock information, reception apparatus 50 may use thedifference information to generate each reference clock.

[Detailed Configuration and Operation Flow]

Here, a functional configuration and operation flow of receptionapparatus 50 will be described. FIG. 32 is a block diagram illustratingthe functional configuration of reception apparatus 50. FIG. 33 is adiagram illustrating the operation flow of reception apparatus 50. Here,the following describes an example in which the reference clockinformation is stored in either one of the IP layer and the transferlayer, and based on the reference clock information in either layer,reception apparatus 50 reproduces the reference clock.

Reception apparatus 50 includes receiver 10, decoder 11, TLVdemultiplexer 12, IP demultiplexer 13, MMT demultiplexer 14,synchronizer 17, and decoding presenter 18. In addition, receptionapparatus 50 includes first reference clock information extractor 15 a,second reference clock information extractor 15 b, first reference clockgenerator 16 a, and second reference clock generator 16 b.

Control information of the transfer layer (such as slot header and TMCC,herein TMCC) stores a flag that indicates whether the reference clockinformation is in the IP layer. In addition, when there is no referenceclock information in the IP layer, the control information of thetransfer layer stores the reference clock information.

In addition, the control information of the transfer layer stores, whenthere is no reference clock information in the IP layer, a flag thatindicates whether the reference clock information acquired in thetransfer layer is necessary for processing in the upper layer, or a flagthat indicates whether the reproduced reference clock information isnecessary for processing in the upper layer.

For example, when the reference clock information is 64-bit NTP, NTP isstored in a 64-bit field that indicates reference clock information. Inaddition, a flag that indicates whether the reference clock informationis in the IP layer may be provided in the field for reference clockinformation. Since the transfer layer does not need to store thereference clock information when the reference clock information isstored in the IP layer, the field may be utilized.

For example, when the reference clock information is in the IP layer anda predetermined value (for example, ALL 1) is in the field for referenceclock information, reception apparatus 50 determines that the value isnot reference clock information but is the flag that indicates that thereference clock information is in the IP layer. Alternatively, a valuebased on a predetermined rule may be used as a flag; for example, whenALL 1 is indicated once in the field for reference clock information,reception apparatus 50 determines that the reference clock informationis in the field, and when ALL 1 is indicated continuously more oftenthan a predetermined number of times, reception apparatus 50 determinesthat the reference clock information is in the IP layer.

Decoder 11 of reception apparatus 50 analyzes TMCC, which is controlinformation, in the transfer layer, and analyzes various flags and thereference clock information (S171). Then, decoder 11 makes adetermination based on the aforementioned flags (S172). When it isdetermined that the reference clock information is not in the IP layer(the reference clock information is in the transfer layer) (No in S172),second reference clock information extractor 15 b acquires (extracts)the reference clock information in the transfer layer, and secondreference clock generator 16 b reproduces (generates) the referenceclock.

Next, decoder 11 makes a determination on whether the reference clockreproduced in the transfer layer is necessary for processing in theupper layer (S174). When it is determined that the reference clockreproduced in the transfer layer is necessary for processing in theupper layer (Yes in S174), second reference clock generator 16 b outputsthe reference clock reproduced in step S174 to the upper layer (S175).When it is not determined that the reference clock reproduced in thetransfer layer is necessary for processing in the upper layer (No inS174), the processing ends.

On the other hand, when it is determined that the reference clockinformation is in the IP layer (the reference clock information is notin the transfer layer) (Yes in S172), decoder 11 does not performacquisition of the reference clock information and reproduction of thereference clock in the transfer layer. In this case, first referenceclock information extractor 15 a and first reference clock generator 16a respectively perform acquisition of the reference clock informationand reproduction of the reference clock in the IP layer (S176).

Note that, when reproduction of the reference clock is not necessary inthe transfer layer, and when the upper layer does not need the referenceclock, decoder 11 does not need to perform acquisition of the referenceclock information and reproduction of the reference clock in thetransfer layer (S173).

In addition, when the reference clock is necessary in the upper layer,instead of outputting the reproduced reference clock, receptionapparatus 50 may pass the reference clock information to the upperlayer, and perform reproduction of the reference clock in the upperlayer. In addition, based on the reference clock reproduced in thetransfer layer, reception apparatus 50 may newly generate referenceclock information, and may output the generated reference clockinformation to the upper layer.

Methods for outputting the reference clock to the upper layer include amethod for outputting the reproduced reference clock as it is, and amethod for storing or converting and outputting the acquired referenceclock information or the newly generated reference clock informationinto data structure to be output to the upper layer.

[Another Example of Operation Flow]

Next, another operation flow of reception apparatus 50 will bedescribed. FIG. 34 is a diagram illustrating another operation flow ofreception apparatus 50. Note that the configuration of receptionapparatus 50 is similar to the configuration of FIG. 32 .

In FIG. 34 , the reference clock information is stored in each of the IPlayer and the transfer layer. When a plurality of pieces of referenceclock information is stored, relative information on precision of thepieces of reference clock information is stored in either layer.

Decoder 11 analyzes TMCC (S181) and makes a determination based on theflags (S182). When it is determined that the reference clock informationis not in the IP layer (No in S182), decoder 11 performs acquisition ofthe reference clock information and reproduction of the reference clockin the transfer layer (S185).

On the other hand, when it is determined in step S182 that the referenceclock information is in the IP layer (Yes in S182), decoder 11determines which of the reference clock information in the transferlayer and the reference clock information in the IP layer has higherprecision (S183). When it is determined that precision of the referenceclock information in the IP layer is higher than precision of thereference clock information in the transfer layer (Yes in S183), decoder11 performs acquisition of the reference clock information andreproduction of the reference clock in the IP layer (S184). When it isdetermined that precision of the reference clock information in the IPlayer is lower than precision of the reference clock information in thetransfer layer (No in S183), decoder 11 performs acquisition of thereference clock information and reproduction of the reference clock inthe transfer layer (S185).

Advantageous Effects, Etc.

As described above, the transmission apparatus may transmit a pluralityof pieces of reference clock information in one or more layers. When theplurality of pieces of reference clock information is transmitted,reception apparatus 50 may select either one piece of the referenceclock information to be used for generation of the reference clock(system clock), and may use both pieces of the reference clockinformation to generate the reference clock. Reception apparatus 50 mayselect high-precision reference clock information, and may selectreference clock information that can be acquired more quickly.

In addition, when the reference clock information is transmitted in aplurality of layers, the transmission apparatus may store informationindicating that the reference clock information is transmitted in theplurality of layers. In addition, the transmission apparatus maytransmit, in the lower layer, information indicating that the referenceclock information is transmitted in the plurality of layers, orinformation related to the layers or protocols in which the referenceclock information is transmitted. Furthermore, the transmissionapparatus may transmit information that indicates a relationship betweenthe pieces of reference clock information stored in different layers.

Reception apparatus 50 can determine that the reference clockinformation is contained in the upper layer during DEMUX processing inthe lower layer, and can decide which reference clock information to usebased on this determination. Reception apparatus 50 may decide whichreference clock information to use based on which layer of referenceclock reproduction reception apparatus 50 supports, and recommendedreference clock reproduction may be specified by broadcasting stationapparatuses.

When the reference clock information is transmitted in the plurality oflayers, reception apparatus 50 may extract the reference clockinformation in the lower layer, and may extract, from the lower layer,the reference clock information contained in the upper layer. Then,reception apparatus 50 may use at least one or more pieces of extractedreference clock information to generate the reference clock.

Here, the transmission apparatus may transmit the plurality of pieces ofreference clock information through a plurality of transfer channels.The transmission apparatus may transmit the plurality of pieces ofreference clock information through the plurality of transfer channels,and may transmit information related to the transfer channels throughwhich the reference clock information is transferred.

OTHER EXEMPLARY EMBODIMENTS

While the exemplary embodiments have been described above, the presentdisclosure is not limited to the aforementioned exemplary embodiments.

For example, it is assumed that, in addition to the conventional 32-bitshort-format NTP contained in the MMT packet header, higher-precisionreference clock information is transmitted. In such a case, thetransmission apparatus further transmits information for allowing thereception apparatus to use the high-precision reference clockinformation to reproduce the 32-bit short-format NTP. The aforementionedinformation is, for example, time information indicating a relativerelationship between clocks, and a configuration for transmitting theinformation by using CRI_descriptor( ), etc. may be considered.

Note that, when the reception apparatus can reproduce the 32-bitshort-format NTP, the reception apparatus does not need the conventionalNTP field contained in the MMT packet header. Therefore, thetransmission apparatus may store another piece of information in the NTPfield, and may perform header compression processing by reducing the NTPfield. When the header compression processing is performed, thetransmission apparatus transmits information indicating that the NTPfield is reduced. When the NTP field is reduced, the reception apparatusgenerates the reference clock by using another piece of reference clockinformation, and reproduces the 32-bit short-format NTP.

In addition, when the MMT packet is transferred using a broadbandtransfer channel, the reception apparatus may use not the referenceclock information but the 32-bit short-format NTP for QoS control.Accordingly, the transmission apparatus does not need to transmit thereference clock information through the broadband transfer channel. Inaddition, when the End-to-End delay of the broadband transfer channel iswithin a certain value, the reception apparatus may use the referenceclock information for clock reproduction.

Note that, although the aforementioned first exemplary embodiment hasdescribed the case where the MMT/IP/TLV scheme is used as an example,schemes other than the MMT scheme may be used as a multiplexing scheme.For example, the present disclosure may also be applied to an MPEG2-TSscheme, RTP (Real-time Transport Protocol) scheme, or MPEG-DASH (DynamicAdaptive Streaming over HTTP) scheme.

In addition, methods for header compression processing of IP packets maybe RoHC (Robust Header Compression) and HCfB (Header Compression forBroadcasting).

Schemes for storing IP packets in broadcast may be a GSE (Generic StreamEncapsulation) scheme and IPoverTS scheme using ULE (UnidirectionalLight-weight. Encapsulation) in addition to the TLV scheme.

The present disclosure may be applied to a case where any of suchschemes is used. Application of the present disclosure allows thereception apparatus to achieve shortening of time to the acquisition ofthe reference clock information and reduction in the processes, and toachieve high precision of the clock by hardware implementation.

Note that, while the reference clock information in the aforementionedexemplary embodiments is NTP when the multiplexing scheme is MMT, forexample, the reference clock information is PCR (Program ClockReference) when the multiplexing scheme is the MPEG2-TS scheme. Inaddition, when the multiplexing scheme is MMT, the transmissionapparatus may transfer PTP prescribed by IEEE 1588 in an NTP form, andmay transfer part of bits of NTP. That is, the reference clockinformation may be information indicating time that is set by thetransmission apparatus. Note that NTP does not mean an NTP value in anNTP server commonly used on the Internet.

In addition, the present disclosure may be implemented as a transmissionapparatus (transmission method) that transmits the transfer slot thatstores the reference clock information by the aforementioned method. Aconfiguration of the transmission apparatus will be supplemented below.FIG. 35 is a block diagram illustrating a functional configuration ofthe transmission apparatus. FIG. 36 is an operation flow of thetransmission apparatus.

In FIG. 35 , transmission apparatus 30 includes generator 31 andtransmitter 32. Note that each component of transmission apparatus 30 isspecifically implemented by a microcomputer, a processor, a dedicatedcircuit, or the like.

Transmission apparatus 30 is specifically a broadcasting server, and isan example of the aforementioned “transmission apparatus” of the firstexemplary embodiment.

Generator 31 generates, for example, a transfer slot that stores aplurality of slots that each store one or more TLV packets that eachstore an IP packet (S151 of FIG. 36 ).

Generator 31 allows the IP packet stored in the TLV packet positioned ata head within the head slot within the transfer slot (hereinafter thisIP packet is also referred to as an object IP packet) to contain thefirst reference clock information, such as NTP, that indicates time forreproduction of content (for example, broadcast content such as videoand voice). The object IP packet is an IP packet that does not undergoheader compression, and the first reference clock information is stored,for example, within the object IP packet in data structure differentfrom data structure of the MMT packet.

In addition, generator 31 stores the second reference clock informationthat indicates time for reproduction of content in control information(TMCC) within the transfer slot.

Specifically, generator 31 includes a coder that codes the broadcastcontent, MMT multiplexer, IP multiplexer, TLV multiplexer, and the like.Here, the TLV packet is an example of a first transfer unit, the slot isan example of a second transfer unit, and the transfer slot is anexample of a transfer frame.

Transmitter 32 transmits the transfer slot generated by generator 31(transfer channel coded data containing the transfer slot) throughbroadcast (S152 of FIG. 36 ).

As also described in the aforementioned exemplary embodiments,transmission apparatus 30 can simplify the processes by which thereception apparatus acquires the reference clock information. Therefore,the reception apparatus can shorten time until acquiring the referenceclock information.

In addition, by the second reference clock information that indicatestime for reproduction of the content being stored in the controlinformation within the frame, the reception apparatus can select whichreference clock information to use from among the first reference clockinformation and the second reference clock information.

Note that in the aforementioned exemplary embodiments, components mayeach include dedicated hardware or may be implemented through executionof a software program suitable for each component. The components may beeach implemented by a program execution unit, such as a CPU and aprocessor, reading and executing the software program recorded in arecording medium such as a hard disk and a semiconductor memory.

In addition, the components may be circuits. These circuits mayconstitute one circuit as a whole, and may be different circuits. Inaddition, each of these circuits may be a general-purpose circuit, andmay be a dedicated circuit.

For example, in each of the aforementioned exemplary embodiments,processes executed by a specific processor may be executed by anotherprocessor. In addition, order of the plurality of processes may bechanged, and the plurality of processes may be executed in parallel.

The reception apparatus (reception method) and transmission apparatus(transmission method) according to one or more aspects have beendescribed above based on the exemplary embodiments. However, the presentdisclosure is not limited to these exemplary embodiments. The presentexemplary embodiments to which various modifications conceivable by aperson skilled in the art are made, and aspects that are made bycombining elements of different exemplary embodiments may also be withinthe scope of the one or more aspects as long as such aspects do notdepart from the gist of the present disclosure.

Although various exemplary embodiments have been described above withreference to the drawings, the present disclosure is of course notlimited to such an example. It will be evident that various changes ormodifications are conceivable by those skilled in the art within thescope described in the appended claims. It is understood that thosechanges or modifications naturally belong to the technical scope of thepresent disclosure. In addition, without departing from the spirit ofthe disclosure, the components in the aforementioned exemplaryembodiments may be appropriately combined.

Although the aforementioned exemplary embodiments have described anexample in which the present disclosure is made using hardware, thepresent disclosure may also be implemented by software in cooperationwith hardware.

In addition, functional blocks used for description of theaforementioned exemplary embodiments are each typically implemented asan LSI, an integrated circuit having input terminals and outputterminals. These may be individually integrated into one chip, and maybe integrated into one chip so as to contain part or all of thefunctional blocks. Although the integrated circuit is an LSI here, theintegrated circuit may be referred to as an IC, a system LSI, a superLSI, and an ultra LSI, depending on a difference in a degree ofintegration.

In addition, a method of circuit integration is not limited to LSI, andcircuit integration may be implemented using a dedicated circuit or ageneral-purpose processor. An FPGA (Field Programmable Gate Array),which is programmable after manufacture of an LSI, or a reconfigurableprocessor, in which connections or settings of circuit cells within theLSI are reconfigurable, may be used.

Furthermore, if an advance in semiconductor technologies or otherrelated technologies yields a circuit integration technology that maysubstitute for LSI, the functional blocks may of course be integratedusing such a technology. For example, adaptation of biotechnology may bepossible.

The transmission method according to the present disclosure is useful asa transmission method capable of reducing the processes for acquiringthe reference clock information by the reception apparatus when the MMTscheme is applied to a broadcasting system.

What is claimed is:
 1. A transmission method comprising: coding videocontent; configuring one or more transfer units that include the codedvideo content; and transmitting the one or more transfer units as atransmission signal, the transmission signal including first controlinformation, second control information, and the one or more transferunits, the first control information including a transmission parameterused for the second control information, and the second controlinformation being provided for each of the one or more transfer units,wherein, in at least one transfer unit among the one or more transferunits, the second control information of the at least one transfer unitcontains first clock information used for reproduction of the videocontent, wherein the first control information indicates that the firstclock information is contained within a header of the at least onetransfer unit and a precision of the first clock information in a unitof time, and wherein a first layer includes the first controlinformation, the second control information, and the one or moretransfer units, and a second layer that is different from the firstlayer includes second clock information.
 2. A transmission apparatuscomprising: generating circuitry that, in operation, codes videocontent, and configures one or more transfer units that include thecoded video content; and transmitting circuitry that, in operation,transmits the one or more transfer units as a transmission signal, thetransmission signal including first control information, second controlinformation, and the one or more transfer units, the first controlinformation including a transmission parameter used for the secondcontrol information, and the second control information being providedfor each of the one or more transfer units, wherein, in at least onetransfer unit among the one or more transfer units, the second controlinformation of the at least one transfer unit contains first clockinformation used for reproduction of the video content, wherein thefirst control information indicates that the first clock information iscontained within a header of the at least one transfer unit and aprecision of the first clock information in a unit of time, and whereina first layer includes the first control information, the second controlinformation, and the one or more transfer units, and a second layer thatis different from the first layer includes second clock information. 3.A reception method comprising: receiving a transmission signal, thetransmission signal including first control information, second controlinformation, and one or more transfer units, the first controlinformation including a transmission parameter used for the secondcontrol information, the second control information being provided foreach of the one or more transfer units, and the one or more transferunits including coded video content, wherein, in at least one transferunit among the one or more transfer units, the second controlinformation of the at least one transfer unit contains first clockinformation used for reproduction of the video content, and wherein thefirst control information indicates that the first clock information iscontained within a header of the at least one transfer unit and aprecision of the first clock information in a unit of time; extractingthe first clock information; and generating a clock for reproducing thevideo content by using the first clock information, wherein a firstlayer includes the first control information, the second controlinformation, and the one or more transfer units, and a second layer thatis different from the first layer includes second clock information. 4.A reception apparatus comprising: receiving circuitry that, inoperation, receives a transmission signal, the transmission signalincluding first control information, second control information, and oneor more transfer units, the first control information including atransmission parameter used for the second control information, thesecond control information being provided for each of the one or moretransfer units, and the one or more transfer units including coded videocontent, wherein, in at least one transfer unit among the one or moretransfer units, the second control information of the at least onetransfer unit contains first clock information used for reproduction ofthe video content, and wherein the first control information indicatesthat the first clock information is contained within a header of the atleast one transfer unit and a precision of the first clock informationin a unit of time; extracting circuitry that, in operation, extracts thefirst clock information; and generating circuitry that, in operation,generates a clock for reproducing the video content by using the firstclock information, wherein a first layer includes the first controlinformation, the second control information, and the one or moretransfer units, and a second layer that is different from the firstlayer includes second clock information.